Hi Len,

It took a long time to work out the best test method.
But I can confirm that the version in the autobuilder fixes the autojack crash once you go into us-controls and save the configuration.

If you upgrade from the old version to the new version with DEV=default still in .config/autojackrc, then run autojack you still get the crash:
$ autojack -h
jackd: no process found
a2jmidid: no process found
Failed to unload module: Module module-jackdbus-detect not loaded
Failed to unload module: Module module-udev-detect not loaded
Failed to unload module: Module module-alsa-card not loaded
--- driver select "alsa"
--- driver param set "capture" -> "none"
--- driver param set "playback" -> "none"
--- driver param set "device" -> "hw:iO2,0,0"
--- driver param set "rate" -> "48000"
--- driver param set "period" -> "1024"
--- driver param set "nperiods" -> "2"
--- start
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Traceback (most recent call last):
  File "/usr/bin/autojack", line 624, in <module>
    main()
  File "/usr/bin/autojack", line 601, in main
    config_start()
  File "/usr/bin/autojack", line 367, in config_start
    start_slave(dev)
  File "/usr/bin/autojack", line 536, in start_slave
    dname, dev, sub = ldev.split(",", 2)
ValueError: not enough values to unpack (expected 3, got 1)

By saving a new config in us-controls with default > DEV=0,0,0
--------------------------------------------------------------

Everything is fine:
$ autojack -h
jackd: no process found
a2jmidid: no process found
Failed to unload module: Module module-jackdbus-detect not loaded
Failed to unload module: Module module-udev-detect not loaded
Failed to unload module: Module module-alsa-card not loaded
--- driver select "alsa"
--- driver param set "capture" -> "none"
--- driver param set "playback" -> "none"
--- driver param set "device" -> "hw:iO2,0,0"
--- driver param set "rate" -> "48000"
--- driver param set "period" -> "1024"
--- driver param set "nperiods" -> "2"
--- start
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Extra internal: 
JACK MIDI <-> ALSA sequencer MIDI bridge, version 8 (7383d268c4bfe85df9f10df6351677659211d1ca) built on Thu Jan  1 01:00:00 1970
Copyright 2006,2007 Dmitry S. Baikov
Copyright 2007,2008,2009,2011,2012 Nedko Arnaudov

Bridge starting...
Using JACK server 'default'
Hardware ports will be exported.
Bridge started
Press ctrl-c to stop the bridge
port created: Midi Through [14] (capture): Midi Through Port-0
port created: Midi Through [14] (playback): Midi Through Port-0
port created: iO 2 [24] (capture): iO 2 MIDI 1
port created: iO 2 [24] (playback): iO 2 MIDI 1

Manually edit file back to DEV=default (naughty!)
-------------------------------------------------

$ autojack -h
jackd: no process found
a2jmidid: no process found
Failed to unload module: Module module-jackdbus-detect not loaded
Failed to unload module: Module module-udev-detect not loaded
Failed to unload module: Module module-alsa-card not loaded
--- driver select "alsa"
--- driver param set "capture" -> "none"
--- driver param set "playback" -> "none"
--- driver param set "device" -> "hw:iO2,0,0"
--- driver param set "rate" -> "48000"
--- driver param set "period" -> "1024"
--- driver param set "nperiods" -> "2"
--- start
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Traceback (most recent call last):
  File "/usr/bin/autojack", line 624, in <module>
    main()
  File "/usr/bin/autojack", line 601, in main
    config_start()
  File "/usr/bin/autojack", line 367, in config_start
    start_slave(dev)
  File "/usr/bin/autojack", line 536, in start_slave
    dname, dev, sub = ldev.split(",", 2)
ValueError: not enough values to unpack (expected 3, got 1)

So us-controls now saves a better default value for new installations, but someone that was already getting the crash will still get it until they save a new configuration, and a person that manually edits the config file will also still get a crash.

Trapping the crash in autojack and printing a suitable error message would be the perfect fix.